How long should you cook a piston engine?

You cannot "cook" a piston engine. It's a mechanical device that requires assembly, maintenance, and operation, not cooking.

It sounds like you might be confused about the term "break-in" which refers to the initial running period for a new engine. During break-in, the engine components wear in slightly, creating a smooth, long-lasting surface.

Here's what you need to know:

* Break-in period: This is a critical step for new engines. It involves running the engine at a controlled speed and load for a specified period.

* Specific instructions: The exact duration and procedures for break-in vary depending on the engine model and manufacturer. Always refer to the manufacturer's instructions for proper break-in.

If you're looking for information about how to maintain or operate a piston engine, please be more specific with your question.